The first step in a new era of global energy production is being taken, with a Japanese attempt to recover vast reserves of frozen methane gas from under the ocean floor.

End of the energy crisis?

Professor Richard Selley

The drilling project began on Friday and is the first commercial offshore attempt but it is fraught with danger. Accidental releases of vast volumes of the buried gas have in the past led to the destruction of oil platforms in the Caspian Sea.

These releases are also a possible explanation for the mysterious disappearances of ships.

"It's horrifically dangerous," said Professor Richard Selley, a gas hydrate expert at the Royal School of Mines, Imperial College, London. "If they drill in with a conventional drill ship and they hit the stuff and destabilise it, all the gas comes bubbling up and the ship will sink.

"The Japanese are the brave souls who are drilling this first commercial test offshore," added Professor Selley. "It may be very easy to avoid the risk of a catastrophic blowout but this is the first to test it."

On stream in two years?

Tatsuya Sameshima, the project's director at the Japan National Oil Company, told BBC News Online that commercial production was not imminent: "It is expected that 10 more years will be required for more research effort on several aspects."

But Professor Selley believes the results of this well will set a likely timescale for the methane coming on stream, and "if the technology works, then they could be producing it commercially very quickly, within 18 months or two years".

Methane gas burns more efficiently and cleanly than any other fossil fuel

The methane is the product of ancient sea-floor bacteria, which fed on plant and animal remains. As the sediments subsided, the pressure increased and the methane and water froze to form gas hydrates.

The cause of the danger is that much of the gas hydrate in the world is close to melting and even a small disturbance can release huge volumes of the gas. When the ice melts, it belches out 160 times its volume in gas.

"The trouble is that you can't run," said Professor Selley, noting that one underwater landslide can set off "huge destabilisation events".

Three kilometres down

The drilling attempt, lead by the Japan National Oil Company, is being made from a semi-submersible oil rig. This is stationed 60 kilometres off Japan's Omae Zaki peninsula over the Nankai Trough.

The water depth in the area is 950 metres but the engineers are aiming to reach a total depth of 2,850 m. The gas hydrates are believed to begin 350 m below the sea floor, based on the analysis of the reflections of sound waves.

The whole research programme which culminates in this well is believed to have cost more than $60m.

Ice that burns

The reason that oil companies are so interested in gas hydrates is the colossal global reserves which are estimated to be 80,000 times greater than those for conventional natural gas.

Earth's gas reserves

Methane: 11.3 million trillion cubic metres

Conventional gas: 144 trillion cubic metres

These figures imply the "end of the energy crisis as we know it", said Professor Selley.

"This year or next year, depending on who you believe, we are at maximum production of conventional petroleum - we are no longer finding oil and gas at the rate at which it is being used up," he said.

The US reserves alone are estimated at 5.7 trillion cubic metres (200 trillion cubic feet) of methane - enough to meet that energy-hungry country's needs for 2,000 years at current rates of use.

Japan has led the way because it has very little oil and gas resources of its own.

Carbon dioxide

But the prospect of a huge, and cheap, source of fossil fuels will alarm those who advocate cutting carbon dioxide emissions to the atmosphere.

"If you believe that global warming is happening and that it is due to burning fossil fuels, then you would be concerned at gas hydrates being burned as an energy source, because they will continue that effect," said Professor Selley.

Oil rigs could drill horizontally under the ocean floor to avoid the danger zones

"But if you have to burn fossil fuels, then methane is the cleanest - you don't get the particulates, sulphur compounds or nasty metals that you get with oil."

As well as Japan, a number of other countries have research programmes in gas hydrates, including the US, Canada, India, Korea and Norway. In the US earlier this year, the House of Representatives science committee passed a bill that would provide $42m over five years for research.

Stirring it up

The key to successful exploitation of gas hydrates, which would change the entire structure of the global energy industry, is the technology.

Syntroleum, a US company based in Oklahoma, has just received a patent for a gas hydrate recovery system. It envisages drilling from a ship which 'hovers' over the drill site, carefully uncorks the reservoir and then pipes the gas aboard. Here, any water is siphoned off and the gas is then compacted into a liquid for easier storage.

Included in the hydrate collection device at the bottom of the well are heating elements and electrodes to melt the hydrates, and an agitator to stir them.

One safer approach which has been suggested is to drill into the gas hydrate from the side. It is now possible to drill horizontally for several kilometres, meaning that the ship or rig is not directly over the danger zone.